There are many products now used for melting ice and snow. These products can be, but are not limited to, hygroscopic salts such as calcium chloride and magnesium chloride; fertilizers such as potassium chloride and urea; and rock salt and non-slip aggregates like sand, cinders and calcined diatomaceous earth absorbents.
These current commercial products have their advantages and disadvantages. For example, the hygroscopic salts are excellent low-temperature melters, but are expensive and cause slippery conditions when overused. Fertilizers cause minimal problems on runoff, as they will aid surrounding vegetation, but as ice melters they have very poor characteristics. Rock salt is inexpensive, will kill vegetation on heavy runoff, and has poor ice melting properties. Aggregates, like sand, do not melt or solubilize, and therefore have difficulty embedding into ice to provide a non-slip surface.
To address some of these disadvantages, blends have been employed, but each ingredient acts independently with little to no synergistic effect. Agglomerates such as shown in our previous patent, U.S. Pat. No. 5,211,869, issued May 18, 1993, the disclosure of which is incorporated herein by reference, have been successful. They are, however, complex in their manufacture and are limited in their ability to synergistically coact with a wide range of base materials.
There are many products used for melting ice and snow. The predominant products are, but not solely limited to, calcium chloride, magnesium chloride, rock salt (sodium chloride), potassium chloride and urea, or mixtures of these various salts.
These ice melters are incapable of melting snow and ice in their solid form. They must form a liquid brine. This brine lowers the freezing point of water and effectively dissolves (melts) ice and snow on contact until it becomes diluted to a concentration where its freezing point is raised near water's.
The sooner the ice melting agent converts to a liquid brine, the sooner the ice melting action starts and the ice and snow hazard can be eliminated. Ice melting speed is clearly a critical safety issue with ice melting agents; therefore time to brine conversion is important.
The natural surface tension of the liquid ice melting brine slows the melting action. Surface tension is that force on the surface of a liquid which tends to diminish the surface area to a minimum. It results because of differences in inter molecular attraction (adhesion) at the surface and in the interior of the liquids; at the surface all of the molecules are attracted inward, while in the interior the attraction is the same in all directions. Surface tension has an important effect on the wetting and penetrating ability of the liquid ice melting brine and its resultant melting volume and melting speed of ice and snow.
To address some of the issues of ice melting-speed, in the past various blends have been employed. For example, it has been thought that the addition of calcium chloride and/or magnesium chloride in a dry blend will improve the melting performance of sodium chloride. This same concept is also employed by spraying on a liquid solution of calcium chloride and/or magnesium chloride onto sodium chloride prior to spreading. The goal of these various mixtures is to utilize the hygroscopic and superior melting characteristics of calcium chloride and/or magnesium chloride to improve those of sodium chloride, potassium chloride and urea. In this regard, see our earlier issued U.S. Pat. No. 5,599,475 of Feb. 4, 1997; U.S. Pat. No. 5,651,915 of Jul. 29, 1997, and U.S. Pat. No. 5,683,619 of Nov. 4, 1997, the disclosures of which are incorporated by reference. Also, agglomerates of these various mixtures have been employed with the purpose of improving ice melting performance, see our U.S. Pat. No. 5,599,475 of Feb. 4, 1997, which also is incorporated by reference. Because of a synergistic effect, these various combinations have met with some success. This success, however, can be improved even more, if the issue of surface tension is addressed.
In particular, speed of melting is a critical and important factor in determining the value of ice melting compositions. The reason for this should be apparent. Ice on surfaces represents a risk, and the quicker the risk is removed, the more effective the ice melter and the higher value it has to the consuming user. The trick, however, is to improve melt speed in an economical and practical and ecologically satisfactory way.
Accordingly, it is a primary objective of the present invention to improve now-used ice melter compositions by an additional additive which is an ice melter compatible surface active agent which significantly reduces the ice melting time when the ice melter is spread over a surface from which ice is to be removed.
Yet another objective of the present invention is to select amongst surface active agents those which are ice melter compatible in terms of their ability to reduce surface tension in the presence of high electrolyte concentrations, and at cold temperatures, i.e., from freezing (0.degree. C. or 32.degree. F.) down to -25.degree. F.
A yet further objective of the present invention is to provide an ice melter composition process of preparation which is efficient, economical, and enhances the ability of the surface active agent to effectively lower ice melt time.
An even further objective of the present invention is to provide an ice melter composition which reduces the surface tension of ice melting brine, allowing it to more quickly penetrate into the ice and snow, thereby increasing its melting speed.
The method and means of accomplishing each of the above objectives as well as others will become apparent from the detailed description of the invention which follows hereinafter.